With President Obama pulling away in polls in key states, GOP nominee Mitt Romney had to cut a bold figure Wednesday night in Magness Arena in Denver.

And he did, coming off as witty, assertive and confident. After a lengthy and bruising Republican primary campaign, the former Massachusetts governor proved he is up to the task of seriously challenging the Democratic incumbent.

What he didn't do was provide the sort of specifics that would give voters a strong sense of what they'd be getting into if they elected him.

The president, who has had to own the specifics of the policies he has enacted, was better at explaining what the next four years of an Obama administration would look like, but fell short on key issues as well.

As expected, the economy and the nation's debt dominated this debate, which was about domestic issues.

We were glad to see the candidates talk at length about tax reform, but unfortunately platitudes and talking points tended to supplant clear policy direction. Romney's mantra that he would balance the budget via tax rate cuts and spending cuts that would stimulate the economy has been widely criticized by tax policy analysts.

The president took Romney to the mat on that issue. In doing so, Obama wasn't the stylistic orator we've come to know. He stumbled a bit here and there, but he was right on in his criticism of his challenger.

"It's arithmetic," the president said. "You cannot cut taxes by $5 trillion, add $2 trillion to defense spending and not affect the middle class." That collective $7 trillion that has to be backfilled before Romney could tackle the debt would assuredly come at the expense of the middle class.

The president, however, missed an opportunity to speak to the shared sacrifice needed to take on the nation's $16 trillion debt. He had no response for why he did not support the Simpson-Bowles plan to reduce the federal debt. Romney was right to press him on that count.

Obama should have supported the bipartisan blueprint for an even-handed but painful menu of spending cuts and revenue enhancements.

It's unfortunate that neither candidate was willing to detail his preferred path to a better fiscal future.

An area in which the candidates differed significantly was on Medicare, the government health insurance program for people 65 and older.

Romney, frankly, did not own the voucher approach that he has championed. Instead, he kept saying Medicare wouldn't change for the people who have it now, and he refused to address how such an approach could undercut the program. That's a shame, since there are voters who believe his plan is a valid path to cut entitlement spending.

Obama was correct in pressing Romney on that point, but came up short in explaining in any detail how he would propose suppressing escalating costs for this program.

We also hoped for more detail on issues such as energy and immigration but were disappointed. Other than taking a swipe at green energy subsidies (Romney) and oil company financial help (Obama), energy got barely any mention at all. Immigration fared worse. It was an important topic that deserved to be discussed.

Nevertheless, with this debate, Romney proved he was up to the job of being president. Now, voters will decide if he should get the job.

The next opportunity for both men to make their cases will come Oct. 16 in a town hall debate at Hofstra University in New York. Judging from Wednesday's performance, it will be a forum in which each candidate has ample room to further demonstrate how he intends to lead the country for the next four years.